Maybe OT, but i remember the "power of tape" when i was 10 in 1987, when an italian public radio broadcasted a full videogame (compressed by "turbo loader") every day and it was possible to record and play it on that beautiful commodore 64!
I seem to recall reading that the BBC did the same for the BBC Micro, although I can't find a reference now. Waiting half an hour for a game to load just to find the tape had got corrupted right near the end ("R Tape Loading Error" on the ZX Spectrum I grew up with) was one of the aspects I less fondly remember!
There was a small rubber sucker attachment that you could stick to a TV screen, with the light pen attached. The BBC (tv station) had a programme (probably MicroLive) that would overlay a flashing block on a small section of the screen. The light pen would read that flashing and you'd have a small program.
I recall seeing a torrent of the full series a while back - I'd like to think that it's probably still possible to decode the programs even today. :)
4 Computer Buffs also transmitted some software as audio, usually over teletext pages or the test card, while the channel was off air - again, see here:
One of the BBC programmes - either 'The Computer Programme' or 'Making The Most Of The Micro' transmitted a BBC Micro program as audio, too, but they intentionally kept it very short so as not to offend viewers who didn't like the noise.
That said, they lengthened the broadcast as a result of transmitting the program at 300 baud - they did tell everyone at home to make sure they typed *TAPE 3 (i.e. to crank the loading speed down to 300 baud rather than the Beeb's normal 1200 baud), presumably to strengthen the chances of some usable data actually making it through. :)
You might be thinking of software on ceefax: they had pages in the high numbers which contained gibberish to the viewer but which could be read by a BBC Micro with teletext adapter
They also, as I remember, used to broadcast data at the top of the picture (possibly just about off-screen) during 'The Computer Programme' or one of its follow-ups, that a BBC Micro could decipher with some kind of dongle.
